The present invention relates to an apparatus and method for determining axis deviation of an on-vehicle radar.
Conventionally, radar is mounted on a vehicle to detect the distance and bearing of a physical object around the vehicle. Japanese Patent Publication Laid-Open (JP-A) No. 2006-275748 discloses an apparatus for determining the amount of axis deviation in the horizontal direction of an on-vehicle radar. According to this apparatus, distribution data of detected static targets is held in time series for a predetermined time period before the present time. Only when it is determined that the vehicle travels straight at both the present time and the predetermine time before, the distribution data obtained at the predetermined time before is integrated. The amount of axis deviation is calculated based on the integrated value.
In the above technique, in order to keep the accuracy of the amount of axis deviation, the distribution data obtained over a predetermined time period before and after the vehicle makes a transition from traveling straight to traveling along a curve or from traveling along a curve to traveling straight is ignored, thereby preventing the integration. Therefore, it is required to accurately determine whether the vehicle is traveling straight or traveling along a curve. Such determination is generally made, for example, by calculating a difference between the wheel speed of the inner wheel and the wheel speed of the outer wheel, or by using a yaw rate sensor. The accuracy of such determination may deteriorate due to an influence of, for example, wheel slip, and temperature or temporal drift of a yaw rate sensor. The deterioration in the accuracy of the determination may influence the detection of the axis deviation of a radar, which may cause an error in the amount of axis deviation.
Therefore, a technique is desired for determining an axis deviation of a radar with higher accuracy, without requiring the above determination.